With advances in ultrasound technologies, ultrasound monitoring devices are increasingly available for home use. With this, the risk of exposure to doses of ultrasound higher than recommended is also increasing. Home ultrasound devices with automatic time out and those that measure the dosage and automatically lock themselves are known. The principle behind safe exposure to any radiation, in the present case to ultrasound radiation, is known as ALARA—As Low As Reasonably Achievable.
The published European patent application EP1852058A1 titled “Fetus Movement Monitoring System and Fetus Movement Information Collecting Device” describes a device for sensing fetal movements that uses a passive sensor. It states that in hospitals, the image of a fetus in the uterus of the mother's body is generally monitored by an ultrasonic wave echo device. But, because this type of device is a so-called active sensor type which applies an ultrasonic wave to a fetus in the uterus of the mother's body and receives its reflected wave, it is undesirable to use this type of device for monitoring fetal movements over a long time in consideration of an adverse influence to the fetus. Furthermore, there is a problem that an ultrasonic wave echo device is configured to be used by a specialist such as a doctor or midwife, and cannot be used easily by a pregnant woman herself at home.
Recent advances in ultrasound technologies have enabled the use of Doppler Ultrasound for fetal movement monitoring at home. However the danger of unintended exposure to ultrasound radiation beyond recommended doses still exists.